And of course detonation is a whole new game. It is not a chamber with progressively burning powder, but a bomb with
the high speed explosion that gun actions can't handle. The quick huge pressure spike that occurs in a 460 Wea size case, if a detonation occurs would need a huge BMG action
to contain it.And maybe not.Ed.

Mike--Yes the 460 the neighbor has got is quit a bit of
metal behind bolt handle.But it doesn't bear any load until the front lugs fail.As the fellow related below about Win 70 he has on the shop, the companies figure that bolt handle will save the shooter in most cases, even if sheared off, if some thing goes wrong.My Enfields are P-14 and that shoulder behind bolt handle is little bigger than on Weatherby, and for my testing I put a bearing surface there.Same for Ruger 77.As for the bolt faces that is
a compression factor that is real large, much more than
what lug shear factor is.IE, before the bolt would crush, you could blow up a barrels 2 times thicker than one regular size actions, if the lugs held.Weatherby used rear locking S&L actions in the 50s with high pressures large cases. S&L sold rifles with 308 Norma and others, at high pressures.Ed.

http://www.thehighroad.org/attachment.php?s=&postid=435056

This is 222 Reminton built by LUX in Germany.
The only thing locking the bolt to bolt thrust is the handle, like a 22 rimfire.

The firing pin hole is huge, and in a incremental load work up, the primers pierce right at max SAAMI pressure. [image]http://www.thehighroad.org/attachment.php?s=&postid=435056.jpg[/image]

Mike, you would have a force to the rear equivalent to the max pressure, say 60,000 psi times the area of the rear of the cartridge (actually a bit less - the internal area) and that is resisted by the shear strenght of the cross sectional area of the bolt handle at the point of resistance. In some cases the bolt might even be able to "notch" out a chunk of metal at the rear of the action. The rest would be resisted by the wood and it would not hold. So you need to examine how the bolt is captured in the action and the cross sectioinal area and we need the shear strenght of the steel and I do not have my steel books home. But that is it in a nutshell. Generally the shear stenght is far above 60,000 psi and if the are of the bolt were in the neighborhood of 75% I would bet it would hold, but if and only if the whole cross sectional area can resist the shear force. If it is just partial then there is more detective work to do.

All that's true for the forces in a stationary situation where the bolt handle was already fully bearing against the supporting surfaces of the receiver, with no lugs resisting the force. But in a situation where the lugs somehow let go, in all likelihood the bolt would have to move somewhat before the handle contacted the receiver. In a moving impact the forces could be substantially higher.

Mike-A large Weatherby case at 60k would develope about
12,000 lbs of thrust on the bolt.The amount of shear a
bolt handle(same formula for lugs also), that is part of the original forging, can handle is the cross section area times 70,000 lbs(at the level bolts are heat treated to).My Enfields and Ruger 77 figure out to about 20,000lbs on handle and about
34,000 on the lugs.That rating on the handle is if it is in contact, not setting away.....If lugs fail and the bolt gets a run at the safety shoulder where the bolt handle sets, who knows what that headstart might cause.
If on failure the bolt cams a little in back travel it may
turn a little out of battery and slip over that safety shoulder.On my test rifles I made both lugs bear even and added third bearing surface on bolt handle just so that it takes load at the same time.It saved my hide once when
needed.IE, I feel that bolt handles or the Mauser third
lug are not most efficient safety if they are setting away
from their abutments.And on the Mark 5 if all the front lugs
are bearing together( which is a goal no one says they have achieved)the shear rating of all those small lugs if they are al working is about 28,000 lbs, less than My Ruger or Enfield.Got this from adding total shear area of all nine lugs, about .4 sg in times 70,000 lbs..Interesting subject
you think?? Ed.

Ed,

Another factor that might also be considered would be bearing area of the lugs.

Would the pressure be there long enough for the bolt handle to let go. Once the bolt did start to move back then the case head would blow which should mean a huge drop in pressure.

Mike

Mike--The trouble of it is is the Rem syndrome, that they
put front of bolt inside of barrel to keep case from rupturing or gas from escaping.And looking at a Weatherby bolt, it does impress you, and makes you wonder how it could fail.But like Ken analysed it, those lugs being thin, in front to back cross section not bearing even, with those early factory heavy loads or heavy handloads, could crack
lugs that beared untill it got to last few.Lugs may crack before they swage back to catch the rest.The ideal is If they swaged back,
instead of cracking then they would be bearing even as they keep going back.But that isn't happening in some cases, some may crack, and then the right
overload shears the ones left.Big lug actions,two or three lugs,ie mauser style,
with overloads, lugs not even, dimple back on the lug bearing first, until they bear even, in most cases.Unless they are really way off.That 75,000 psi loading level can
have the one in a thousand that goes way up, or with temperature extremes in the shooting areas, one in 25 may go way high.Ed.

Ed,

I just went and looked at a 416. There is a lot metal behind that bolt handle. I can't remember clearly how big the rear lug area is on a 303 SMLE but I don't remember it be a lot bigger.

Another factor I have often wondered about is the sheer area involved with bolt faces.

Mike

As we speak I have in my shop a Win 70 (post 64) that lost it all. Sheared the bolt lugs off AND THEN sheared the bolt handle off!! I think the bolt handle slowed the bolt body down enough that it didn't kill the guy. IMPRESSIVE!!

I have a Lux in 22 hornet neat little rifle but not very strong. the action developed excess head space in about 200 hornet rounds. I made a new bolt handle made and welded the action back up I only shoot very light cast bullet loads at 22 rf vel. Seems to be holding but I don't shoot it much.

Jim,

What report did you get from the shooter of this gun? Was he using handloads? Did he use the wrong ammo for the gun? Was there a barrel obstruction? Finally, how is the shooter? Did he sustain trauma?

Roger QSL

He actually got off pretty easily. When he woke up he got up and starting putting stuff back in his truck. Then he noticed the bleeding and decided to get to town and the doctor. The worst thing I heard, was they had to leave a small piece of metal in his sinuses somewhere. Didn't loose either eye! His vision (not shooting) glasses were knocked off. They found the left side and the right earpiece but none of the right lens. What was left of his glasse and the bolt handle were found almost 30 feet from where he was sitting. The rear tang was bent down and left, from the bolt handle trying to be a lug, and the rear reciever ring is cracked. The stock, from the pistol grip to the front action screw, is just kindling. He got off easy, and should send Winchester a nice thank you letter!

He was shooting handloads. Some guys pulled a bunch of them and there was a LOT of variation in charge weight. He could not have accomlished this if he had dipped the cases full and stuffed a bullet on top. What they did find were a couple that were 40 grains LIGHT of the load he said he was using. Belk and everyone I show it to suspect a detonation.

There are some good notes about calculating pressure to bolt handle shear, but I would add Ackley's point that the force to stretch or slip the brass that grips the chamber walls need to be subtracted. That extra element is why so many chambers fail and so few breeches fail.

Clark-In the figures I posted above there is a factor in the math to account for the part of the thrust that the
brass case holds.Ed.

Ricochet, Mike's question stipulated that the lugs had been machined off the bolt and were no longer in place and that is why I disregarded them.

Ed Hubel: Not a complaint, just hoping to learn somthing.

How did you allow for the brass holding?. "varmit Al" has done a finite element analysis

that shows the brass releasing at a given pressure. My own experimenting has been with

a chamber with some headspace using oiled/ dry cases. It seems that adry case will stay

forward up to around 40KPSI then come back with the same force oiled or not. Pressure

sensing tape seems to comfirm this, but I am planning better control for the next tests.

There seems to be a lot of unpublished information out there on blow ups, perhaps a

central site for the information could be created.

ask the troll.. I am certain it knows about blowing up actions

jeffe

"Handbook for Shooters and Reloaders" Vol. 1 1962 P.O.Ackley
Chapter 7 "Pressure" page 140
"To further illustrate this principal, and old, discarded, beat up Winchester Model 94 rifle was resurrected from the junk pile. The barrel was rechambered for the "improved" 30-30 with a 40 [degrees] shoulder and minimum body taper... [Ackley went on to get case separation with factory 30-30 ammo in a an oiled improved chamber with the barrel unscrewed 2 turns, but with a dry chamber the case formed but did not separate]"
Chapter 7 "Pressure" page 147
"To further prove the point, the locking lug was removed from the action entirely leaving the breech block or bolt with no means of support other than the finger lever. See illustrations. The rifle was fired several times with the barrel tight. All cases appeared to be normal except for excessive primer protrusion. Now to state that this action will handle only certain pressers, or that the brass case will not support any amount of pressure seems to be out of order. There is plenty of room for further testing along these lines but the tests described seem to indicate that a very small percentage of the CHAMBER pressure was transferred to the breech bolt in the form of thrust. In this test the barrel absorbed the pressure while the action merely furnish the means for detonating the cartridge except when the chamber was oily.

The other illustration shows a Model 94 which was accidentally blown up. The load was supposedly 16 grains of Unique behind a 150 grain case bullet. A double charge was inadvertently thrown with the results shown. The action was not damaged except for threads being expanded when the chamber section of the barrel split. The barrel separated completely just forward of the chamber, the bullet passing downward severing the magazine tube and blowing the forearm to pieces. The shooter was not injured. This shows the high pressure could not be contained by the barrel but hat relatively straight standard .30/30 case did not back up against the breech bolt enough to harm ay of the action parts. The receiver has since been replaced and rifle works perfectly"

A friend of mine had his Tikka 6.5x55 "explode" last year. The area around the throat/chamber bulged, the magazine and associated metal /plastic was blown out and completely destroyed and the stock end up in four major pieces; front, back and two side pieces from either side of the magazine area, plus lots of sharpnel. The bolt sheared as if somebody had sliced a slither of one side including one of the locking lugs but luckily for him it seems this "shearing" caused the bolt to jam in the action. A gun smith tried to open the bolt using finger pressure and the bolt handle fell off under virtually no pressure at all...We never did find out what caused this explosion but I post it here as an example of another way a rifle can fail....I do realise that tikka bolts are not one piece...



Regards,



Pete

Irv-With proper headspace the brass will hold its
share of the load, and bolt the rest.For easy math I multiply the base area of the case times pressure times 2/3.
The 1/3 left accounts for the thickness of the brass sides
and the load the brass is holdingThe figures I get are very close to lab thrust results and what others have found out over the years.When you say the case is coming back with force it is really stretching at the 40,000 lbs and above.
If headspace is tight, that flexing is minimal and you don't get case sidewall thinning.You are right about us needing good info on action safety and design.The total overall shear of the 9 Weatherby lugs is less than the shear for example, of a Savage.Each Wea lug has a shear on average of 3400 lbs.If only a third or half of the nine are bearing even, and big base WEA cases are putting 12-14000
lbs of thrust on the bolt, there is not enough multiples
of safety margin.And I think those small lugs stress crack rather than swage back.If they swaged back then they would pick up the rest and action could hold more.If they cracked it moves back to next and cracks them, and then overload(from whatever cause)
shears off last ones and bolt handle has to catch it.If bolt
handle which is a forging may be the one in 20,000 with say
a weakness or fault...........Who Knows.Ed.